An ink jet recording method is a method wherein droplets of a recording fluid containing a water-soluble dye such as a direct dye or an acid dye are jetted from fine discharge orifices, and it is a recording method whereby high speed recording or multi color image recording is possible. The recording fluid is required to quickly fix to recording sheets commonly used for the office work, such as PPC (plain paper copier) sheets for electrophotography or fan hold sheets (continuous paper for e.g. computers) and yet to present a good printing quality for the printed matter i.e. to present a sharp profile of printed letters without bleeding, and the recording fluid is also required to be excellent in the stability during storage. Accordingly, the solvent which may be used for the recording fluid, is very limited.
Further, with respect to the dye for the recording fluid, it is required to have an adequate solubility in the solvent which is limited as described above, and it is also required that even when stored for a long period of time in the form of a recording fluid, it is stable, and the saturation and density of the printed image are high, and yet, it is excellent in water resistance, light resistance and ozone resistance.
Thus, in a conventional yellow color recording fluid (ink), a common dye such as direct yellow 132, direct yellow 86 or acid yellow 23, as disclosed in the color index, has been used. However, these dyes have had a problem that the image tends to fade under irradiation with light i.e. the light resistance is poor.
As a method for solving this problem, e.g. JP-A-57-42775 proposes a recording fluid containing a specific metal complex dye of the type where a metal is coordinated in the vicinity of an azo group. The metal complex dye exemplified there is one prepared by using, as a diazo component, a specific 6-membered cyclic aromatic compound having either a carbon atom possessing an orthohydroxyl group, or a nitrogen atom to form a coordination bond and using, as a coupling component, a 5-membered cyclic pyrazole derivative having a hydroxy group on the carbon adjacent to the carbon bonded to the azo group. It is certainly expected that if such a dye is employed for ink jet recording, the light resistance will be improved as compared with the above-mentioned common dyes. The present inventors have earlier proposed a recording fluid containing a metal complex dye of this type having the water resistance or light resistance improved (JP-A-2-80470). However, the metal complex dye of the above-mentioned type tends to be inferior to the conventional common dye in the gas resistance which has recently become important in order to preserve an ink jet image. Such an inferior performance tends to be more distinct in an image formed on an ink jet sheet dedicated to obtain an image like a photograph, which has been remarkably progressed in the last few years. Accordingly, a dye satisfying both light resistance and gas resistance has been desired more than ever.
Here, the gas resistance is a nature to prevent an undesirable phenomenon such that the dye tends to fade by a gas which becomes various active species, such as a nitrogen oxide, a sulfur oxide, other acidic gas or ozone, in air. This fading phenomenon by gas is known to have a high interrelation with an accelerated test wherein an image is exposed to e.g. an air containing ozone at a concentration of 3 ppm or 10 ppm. Accordingly, the gas resistance is commonly reworded as ozone resistance. Also in this specification, as an index of gas resistance, a parameter obtained by evaluating the degree of fading of a test specimen subjected to exposure to ozone (i.e. an evaluation result of ozone resistance) will be used hereinafter for evaluation.
Further, JP-A-11-293168 discloses examples of a compound prepared by using, as a diazo component, a specific aromatic compound having a carbon having a hydroxyl group adjacent to the carbon bonded to the azo group or a specific aromatic compound having a carbon substituted with a sulfo group adjacent to the carbon bonded to the azo group and using, as a coupling component, a pyrazole derivative as a 5-membered ring or a pyridone-derivative as a 6-membered ring, similar to the dye disclosed in the above-mentioned JP-A-57-42775. This publication clearly describes that it is possible to obtain a vivid magenta dye with the value a* representing a reddish color being at least 50 and with the value b* representing yellowish color being in the vicinity of 0, which is excellent in light resistance. However, in this publication, nothing is disclosed with respect to the ozone resistance of the dye, and such a dye is also considered to be poor in ozone resistance, as is often the case with a compound wherein a coordinate bond is formed via a hydroxyl group of the diazo component.
Further, JP-A-10-072560 proposes a specific metal complex dye of the type wherein a metal is dicoordinated with a part of a coupler i.e. not in the vicinity of the azo group. The characteristic of the metal complex dye exemplified here is that the metal coordinate bond is not present in the vicinity of a so-called chromophoric group such as an azo group or a methine group, but it forms a dicoordinated or higher coordinated bond at a site distanced from there. It is reported that as a result, a dye having a highly vivid color and yet having high light resistance, was obtained. However, nothing is disclosed with respect to the gas resistance.
In addition, in order to form a full color image by an ink jet recording method, it is common to use inks with three primary colors of yellow (Y), magenta (M) and cyan (C) or inks with four colors having black (Bk) added thereto, and to control the discharge amounts of the respective inks, so that such colors are mixed on the recording material to form an image. With respect to fading of such a full color image, it is desired that the fading balance of the primary colors constituting such a color is uniform, but when common dyes such as direct yellow 132, direct yellow 86 and acid yellow 23 disclosed in the above-mentioned color index are used as the yellow color to be used in a conventional dye ink set, they had a problem such that a red or green image obtained in a case where they are used in combination with a magenta dye or a cyan dye to form the color image, is likely to undergo a color change.
It is an object of the present invention to provide a water-soluble complex dye which is excellent in light resistance and ozone resistance and yet capable of forming an image having high saturation in an ink jet recording method; a water-based recording fluid, particularly an ink jet recording fluid, employing such a dye; and an ink set employing such a recording fluid, as well as an ink jet recording method.